In building construction, and in steel-framed building construction in particular, metal bar joists and wide flange beam joists are used as roof framing, typically under corrugated roof decking. The metal bar joists or beams are also used to hang such items as lighting fixtures, sprinkler header assemblies, product conveyors, skylights, HVAC equipment, drywall for ceilings, and the like. For large equipment components, such as some air conditioning units, it is necessary to cut through sections of the corrugated roof decking to form an opening sized to receive the large equipment. Openings are also formed by cutting through sections of roof decking for other purposes, such as to create roof access openings.
In order to reinforce the weakened roof decking above the joist structure once such openings are formed, the typical practice is to weld angle clips to bar joists at panel points to support welded angle framing steel. Panel points are locations just above the apex of a structural bar element that depends downwardly, at an angle, from the upper pair of angle irons of metal bar joists. These zigzagging diagonal bar elements form a truss support structure.
Equipment may be set on a roof deck having greater weight than the decking can support, but within the capacity of the roof joist structure. There is a need to reliably transfer such loads from the decking to the bar joists or beams.
The conventional practice of welding clips to support welded angle framing steel has several drawbacks. For instance, the welding may cause unintended structural damage to the remaining length of the joists through undercutting; the welding may have to be performed from awkward angles, with limited space constraints, making the welding difficult or dangerous; and the welding must be performed by skilled certified welders.
Another common way to install pieces of framing angle between joists is to cut out a section from each end of a 90°-shaped piece of metal, so that one flat surface remains on each end. This flat surface then rests on top of each parallel running joist, with the cut surface extending downward, to be used for mounting equipment. However, such a support angle would need to be installed before the decking. There can also be other problems associated with this arrangement. For example, any time material is removed from a structural component, such as a framing angle, it will then become weakened and will be less capable of supporting loads. Also, stress will tend to be concentrated along the line where the edge of the top flange of the joist meets the non-cut side of the framing angle. As a direct result of this non-uniform, poorly-distributed load, the top flange of the joist can end up bending, and this can lead to roof failure.
As demonstrated in the following sections, a support system is disclosed that can be secured in place at strategic locations along joists, under the corrugated roof decking, as a more reliable solution to reinforcing roofing structure in the vicinity of openings formed in roof decking. The solution is also useful to transfer loads to bar joists or beams in roofing structures where no openings are formed. For example, the support system of the present disclosure may be employed where structural reinforcement is necessary in order to support loads above or below particular locations in the roof, such as for heavy air conditioning condenser units, lighting fixtures, ceiling fans, article conveyors, or the like.